Detection of Vortex Tubes in Solar Granulation from Observations with SUNRISE

The Astrophysical Journal Letters (Impact Factor: 5.6). 10/2010; 723(2):L180. DOI: 10.1088/2041-8205/723/2/L180
Source: arXiv

ABSTRACT We have investigated a time series of continuum intensity maps and corresponding Dopplergrams of granulation in a very quiet solar region at the disk center, recorded with the Imaging Magnetograph eXperiment (IMaX) on board the balloon-borne solar observatory SUNRISE. We find that granules frequently show substructure in the form of lanes composed of a leading bright rim and a trailing dark edge, which move together from the boundary of a granule into the granule itself. We find strikingly similar events in synthesized intensity maps from an ab initio numerical simulation of solar surface convection. From cross sections through the computational domain of the simulation, we conclude that these granular lanes are the visible signature of (horizontally oriented) vortex tubes. The characteristic optical appearance of vortex tubes at the solar surface is explained. We propose that the observed vortex tubes may represent only the large-scale end of a hierarchy of vortex tubes existing near the solar surface.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Advances in solar instrumentation have led to a widespread usage of time series to study the dynamics of solar features, specially at small spatial scales and at very fast cadences. Physical processes at such scales are determinant as building blocks for many others occurring from the lower to the upper layers of the solar atmosphere and beyond, ultimately for understanding the bigger picture of solar activity. Ground-based (SST) and space-borne (Hinode) high-resolution solar data are analyzed in a quiet Sun region displaying negative polarity small-scale magnetic concentrations and a cluster of bright points observed in G-band and Ca II H images. The studied region is characterized by the presence of two small-scale convective vortex-type plasma motions, one of which appears to be affecting the dynamics of both, magnetic features and bright points in its vicinity and therefore the main target of our investigations. We followed the evolution of bright points, intensity variations at different atmospheric heights and magnetic evolution for a set of interesting selected regions. A description of the evolution of the photospheric plasma motions in the region nearby the convective vortex is shown, as well as some plausible cases for convective collapse detected in Stokes profiles.
    04/2014; 290(2).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Spontaneous formation of self-organized magnetic structures, such as sunspots and pores, is one of intriguing and oldest problems, which represents a complicated interaction of convection and magnetic fields on different scales. Observations of sunspots and pores formation reveal a fast process of accumulation of emerging magnetic field into stable long-living magnetic structures. However, the physical mechanisms of the flux accumulation into the compact magnetic structures with high field strength and their stability are not clear. Development of observational capabilities, theory, and realistic-type MHD numerical simulations open a new level of our understanding of the turbulent processes of the magnetic field accumulation. I discuss the recent progress in observations and radiative MHD simulations that provide important clues for possible mechanisms of formation and stability of sunspots and pores, and their links to the dynamo process.
    Proceedings of the International Astronomical Union 08/2012; 8(S294).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the quiet Sun, magnetic fields are usually observed as small-scale magnetic elements, `salt and pepper', covering the entire solar surface. By using 3D radiative MHD numerical simulations we demonstrate that these fields are a result of local dynamo action in the top layers of the convection zone, where extremely weak `seed' magnetic fields can locally grow above the mean equipartition field (e.g., from a $10^{-6}$ G `seed' field to more than 1000 G magnetic structures). We find that the local dynamo action takes place only in a shallow, about 500 km deep, subsurface layer, from which the generated field is transported into deeper layers by convection downdrafts. We demonstrate that the observed dominance of vertical magnetic fields at the photosphere and the horizontal fields above the photosphere can be explained by multi-scale magnetic loops produced by the dynamo.

Full-text (2 Sources)

Available from
May 21, 2014